Multi-mode interference waveguide for light absorption efficiency
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Solution Overview
Problem
Existing light receiving elements face challenges in enhancing light absorption efficiency due to the expansion of signal light intensity distribution orthogonal to the signal light travel direction, leading to inefficient absorption of incident light in the photodetection portion.
Innovation Solution
Incorporating a multi-mode interference (MMI) waveguide with a width larger than the waveguide core, where the length from the input end of the MMI waveguide to the photodetection portion is set between (N−0.3)×100% and N×100% of the shortest length for self-imaging, ensuring the self-imaging point is positioned below the absorption layer, thereby converging more signal light for absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If signal light propagates through a conventional waveguide structure, then the device structure is simple, but the light absorption efficiency is low due to expansion of signal light intensity distribution orthogonal to the signal light travel direction
Solution Approach 1:
The waveguide structure is segmented into two distinct portions: a conventional waveguide portion for signal transmission and a multi-mode interference waveguide portion for light concentration. This segmentation allows each portion to perform its specialized function optimally while maintaining overall device simplicity.
Solution Approach 2:
The multi-mode interference waveguide acts as an intermediary component between the conventional waveguide and the photodetection portion. It receives signal light from the conventional waveguide and transforms its intensity distribution before delivering it to the photodetection portion, thereby improving light absorption efficiency.
2Loss of energy
If the width of the waveguide core is increased to capture more light, then the light absorption efficiency improves, but the device area increases
Solution Approach 1:
Instead of increasing the waveguide core width in the lateral dimension, the invention uses the multi-mode interference waveguide to manipulate light distribution in the vertical dimension through controlled interference patterns. This achieves light concentration without increasing the lateral footprint of the device.
Solution Approach 2:
The invention changes the length parameter of the multi-mode interference waveguide to a specific range ((N−0.3)×100% to N×100% of the self-imaging length) to achieve optimal light concentration. This parameter optimization allows efficient light absorption without increasing device area.
3Loss of energy
If a multi-mode interference waveguide is added to improve light absorption, then the light absorption efficiency increases, but the device complexity increases
Solution Approach 1:
The multi-mode interference waveguide portion is merged with the conventional waveguide structure, sharing common layers such as the waveguide core layer and upper clad layer. This integration reduces the number of discrete components and simplifies the overall device structure while maintaining the light concentration function.
Solution Approach 2:
The multi-mode interference waveguide serves multiple functions: it acts as a transition element between different waveguide sections, a light concentration mechanism through self-imaging, and a coupling structure to the photodetection portion. This multi-functionality reduces the need for additional separate components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly increases light absorption efficiency by maintaining signal light in a convergence direction within the photodetection portion, reducing radiated light outside the absorption layer and enhancing quantum efficiency compared to traditional designs.
Implementation Method 1
the length from the input end of the MMI waveguide to the photodetection portion is set between (N−0.3)×100% and N×100% of the shortest length for self-imaging, ensuring the self-imaging point is positioned below the absorption layer
Implementation Method 2
the absorption layer being disposed above the first semiconductor layer and being configured to absorb the second light
Implementation Method 3
photocarriers (holes and electrons) generated through light absorption in the i-type absorption layer 103 are detected
Data Source
AI summary
A light receiving element includes a waveguide that includes a waveguide core, a multi-mode interference waveguide that has a width larger than a width of the waveguide, the multi-mode interference waveguide receiving a first light from the waveguide core at a first end, and a photodetection portion that includes a first semiconductor layer and an absorption layer disposed on the first semiconductor layer, the first semiconductor layer including at least one layer and receiving a second light from the multi-mode interference waveguide at a second end, the absorption layer being disposed above the first semiconductor layer and absorbing the second light. A distance from the first end of the multi-mode interference waveguide to the second end of the photodetection portion is longer than 70% of a first length and shorter than 100% of the first length, the first length being a length where self-imaging occurs in the multi-mode interference waveguide.